最近有业务需求要在高并发下保持web应用的高性能，具体的业务中是在nginx来反向代理tomcat集群的基础上，做了三次实验：一种情况是使用nginx的proxy_cache来做缓存，经测试，性能最佳；第二种是使用nginx来做动静分离，经测试，性能次于第一种，第三种是使用nginx的proxy_cache来做缓存，同时在nginx的前端使用keepalived来实现nginx的failover切换，即HA。
参考博文一：nginx实现动静分离:http://quenlang.blog.51cto.com/4813803/1570477
参考博文二：nginx使用proxy_cache做缓存:http://quenlang.blog.51cto.com/4813803/1570352
测试工具使用apache的httpd-tools工具，首先在hadoop1上安装该工具，该工具提供ab命令
[root@hadoop1 ~]# yum install httpd-tools -yab命令的参数如下：
-n：请求总数
-c：每次访问的并发数
如：ab -n 50000 -c 10000 http://192.168.0.101/shop/index.html
1、首先测试html静态页面
测试nginx实现web缓存高并发访问下的性能，共5000个请求，每次并发1000，用时0.583秒，IO吞吐量为330.699M/s
[root@hadoop1 ~]# ab -n 5000 -c 1000 http://192.168.0.101/shop/index.html
Server Software: nginx/1.7.6
Server Hostname: 192.168.0.101
Server Port: 80
Document Path: /shop/index.html
Document Length: 192 bytes
Concurrency Level: 1000
Time taken for tests: 0.583 seconds
Complete requests: 5000
Failed requests: 4200
(Connect: 0, Receive: 0, Length: 4200, Exceptions: 0)
Write errors: 0
Non-2xx responses: 819
Total transferred: 197305366 bytes
HTML transferred: 195812742 bytes
Requests per second: 8581.54 [#/sec] (mean)
Time per request: 116.529 [ms] (mean)
Time per request: 0.117 [ms] (mean, across all concurrent requests)
Transfer rate: 330699.98 [Kbytes/sec] received测试nginx实现动静分离高并发访问下的性能，共5000个请求，每次并发1000，用时3.106秒，IO吞吐量为74.187M/s
[root@hadoop1 ~]# ab -n 5000 -c 1000 http://192.168.0.100/shop/index.html
Server Software: nginx/1.7.6
Server Hostname: 192.168.0.100
Server Port: 80
Document Path: /shop/index.html
Document Length: 46428 bytes
Concurrency Level: 1000
Time taken for tests: 3.106 seconds
Complete requests: 5000
Failed requests: 0
Write errors: 0
Total transferred: 235926480 bytes
HTML transferred: 234298640 bytes
Requests per second: 1609.99 [#/sec] (mean)
Time per request: 621.122 [ms] (mean)
Time per request: 0.621 [ms] (mean, across all concurrent requests)
Transfer rate: 74187.39 [Kbytes/sec] received测试不通过nginx代理，直接高并发访问后端tomcat时的性能，共5000个请求，每次并发1000，用时3.532秒，IO吞吐量为65.928M/s
[root@hadoop1 ~]# ab -n 5000 -c 1000 http://192.168.0.103:8080/shop/index.html
Server Software: Apache-Coyote/1.1
Server Hostname: 192.168.0.103
Server Port: 8080
Document Path: /shop/index.html
Document Length: 46428 bytes
Concurrency Level: 1000
Time taken for tests: 3.532 seconds
Complete requests: 5000
Failed requests: 0
Write errors: 0
Total transferred: 238450924 bytes
HTML transferred: 236978956 bytes
Requests per second: 1415.62 [#/sec] (mean)
Time per request: 706.405 [ms] (mean)
Time per request: 0.706 [ms] (mean, across all concurrent requests)
Transfer rate: 65928.82 [Kbytes/sec] received可见，针对html静态页面而言，nginx作为web缓存时的性能要远远优于nginx作为动静分离时的性能，而nginx作为动静分离时的性能略优于不使用nginx代理而直接访问后端tomcat的性能。
2、接着测试图片
测试nginx实现web缓存高并发访问下的性能，共5000个请求，每次并发1000，用时2.155秒，IO吞吐量为935.765M/s
[root@hadoop1 ~]# ab -n 5000 -c 1000 http://192.168.0.101/shop/QQ.jpg
Server Software: nginx/1.7.6
Server Hostname: 192.168.0.101
Server Port: 80
Document Path: /shop/QQ.jpg
Document Length: 192 bytes
Concurrency Level: 1000
Time taken for tests: 2.155 seconds
Complete requests: 5000
Failed requests: 3919
(Connect: 0, Receive: 0, Length: 3919, Exceptions: 0)
Write errors: 0
Non-2xx responses: 1081
Total transferred: 2064708785 bytes
HTML transferred: 2063553225 bytes
Requests per second: 2320.48 [#/sec] (mean)
Time per request: 430.945 [ms] (mean)
Time per request: 0.431 [ms] (mean, across all concurrent requests)
Transfer rate: 935765.00 [Kbytes/sec] received测试nginx实现动静分离高并发访问下的性能，共5000个请求，每次并发1000，用时24.867秒，IO吞吐量为96.387M/s
[root@hadoop1 ~]# ab -n 5000 -c 1000 http://192.168.0.100/shop/QQ.jpg
Server Software: nginx/1.7.6
Server Hostname: 192.168.0.100
Server Port: 80
Document Path: /shop/QQ.jpg
Document Length: 525861 bytes
Concurrency Level: 1000
Time taken for tests: 24.867 seconds
Complete requests: 5000
Failed requests: 371
(Connect: 0, Receive: 0, Length: 371, Exceptions: 0)
Write errors: 0
Non-2xx responses: 352
Total transferred: 2454418691 bytes
HTML transferred: 2453209149 bytes
Requests per second: 201.07 [#/sec] (mean)
Time per request: 4973.454 [ms] (mean)
Time per request: 4.973 [ms] (mean, across all concurrent requests)
Transfer rate: 96387.47 [Kbytes/sec] received测试不通过nginx代理，直接高并发访问后端tomcat时的性能，共5000个请求，每次并发1000，结果发现多次测试都无法成功，也就是说直接
访问后端，后端的tomcat是无法承担起这么高的并发访问压力
[root@hadoop1 ~]# ab -n 5000 -c 1000 http://192.168.0.104:8080/shop/QQ.jpg
Benchmarking 192.168.0.104 (be patient)
Completed 500 requests
Completed 1000 requests
Completed 1500 requests
Completed 2000 requests
apr_socket_recv: Connection reset by peer (104)
Total of 2027 requests completed
[root@hadoop1 ~]# ab -n 5000 -c 1000 http://192.168.0.104:8080/shop/QQ.jpg
Benchmarking 192.168.0.104 (be patient)
Completed 500 requests
Completed 1000 requests
Completed 1500 requests
Completed 2000 requests
Completed 2500 requests
Completed 3000 requests
Completed 3500 requests
apr_socket_recv: Connection reset by peer (104)
Total of 3756 requests completed
[root@hadoop1 ~]# ab -n 5000 -c 1000 http://192.168.0.104:8080/shop/QQ.jpg
Benchmarking 192.168.0.104 (be patient)
Completed 500 requests
Completed 1000 requests
apr_socket_recv: Connection reset by peer (104)
Total of 1198 requests completed可见，针对图片而言，nginx作为web缓存时的性能要远远优于nginx作为动静分离时的性能，而nginx作为动静分离时的性能又要大大优于不使用nginx代理而直接访问后端tomcat的性能。
3、测试jsp动态程序
测试nginx实现web缓存高并发访问下的性能，共2600个请求，每次并发1000，用时34.936秒，IO吞吐量为0.263M/s，整个过程，tomcat后台日志中无错误信息抛出
[root@hadoop1 ~]# ab -n 2600 -c 1000 -k http://192.168.0.101/shop/admin/login.jsp
Server Software: nginx/1.7.6
Server Hostname: 192.168.0.101
Server Port: 80
Document Path: /shop/admin/login.jsp
Document Length: 192 bytes
Concurrency Level: 1000
Time taken for tests: 34.936 seconds
Complete requests: 2600
Failed requests: 1568
(Connect: 0, Receive: 0, Length: 1568, Exceptions: 0)
Write errors: 0
Non-2xx responses: 1033
Keep-Alive requests: 1567
Total transferred: 9421232 bytes
HTML transferred: 8762752 bytes
Requests per second: 74.42 [#/sec] (mean)
Time per request: 13437.110 [ms] (mean)
Time per request: 13.437 [ms] (mean, across all concurrent requests)
Transfer rate: 263.35 [Kbytes/sec] received测试nginx实现动静分离高并发访问下的性能，共2600个请求，每次并发1000，用时58.147秒，IO吞吐量为0.248M/s，这时tomcat的后台日志中抛出大量应用程序的错误日志，说明应用已经开始出错
[root@hadoop1 ~]# ab -n 2600 -c 1000 -k http://192.168.0.100/shop/admin/login.jsp
Server Software: nginx/1.7.6
Server Hostname: 192.168.0.100
Server Port: 80
Document Path: /shop/admin/login.jsp
Document Length: 5462 bytes
Concurrency Level: 1000
Time taken for tests: 58.147 seconds
Complete requests: 2600
Failed requests: 32
(Connect: 0, Receive: 0, Length: 32, Exceptions: 0)
Write errors: 0
Non-2xx responses: 32
Keep-Alive requests: 2568
Total transferred: 14818864 bytes
HTML transferred: 14032560 bytes
Requests per second: 44.71 [#/sec] (mean)
Time per request: 22364.327 [ms] (mean)
Time per request: 22.364 [ms] (mean, across all concurrent requests)
Transfer rate: 248.88 [Kbytes/sec] received测试不通过nginx代理，直接高并发访问后端tomcat时的性能，共2600个请求，每次并发1000，结果发现多次测试都无法成功，也就是说直接访问后端，后端的tomcat是无法承担起这么高的并发访问压力
[root@hadoop1 ~]# ab -n 2600 -c 1000 -k http://192.168.0.102:8080/shop/admin/login.jsp
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 192.168.0.102 (be patient)
apr_socket_recv: Connection reset by peer (104)
Total of 100 requests completed
[root@hadoop1 ~]# ab -n 2600 -c 1000 -k http://192.168.0.102:8080/shop/admin/login.jsp
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 192.168.0.102 (be patient)
apr_socket_recv: Connection reset by peer (104)
Total of 57 requests completed
[root@hadoop1 ~]# ab -n 2600 -c 1000 -k http://192.168.0.102:8080/shop/admin/login.jsp
This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 192.168.0.102 (be patient)
apr_socket_recv: Connection reset by peer (104)可见，针对jsp动态程序而言，尽管nginx的配置没有缓存动态程序，但nginx作为web缓存时的性能还是要远远优于nginx作为动静分离时的性能，而nginx作为动静分离时的性能又要大大优于不使用nginx代理而直接访问后端tomcat的性能。
5、结论
测试结果显示，尽管nginx动静分离可以提高web的性能，确实如此，相比于直接访问tomcat来说，动静分离能够大幅度提高站点的并发访问性能。但是这种架构跟nginx反向代理tomcat集群的同时使用自身proxy_cache模块来作为web站点的缓存服务器的情形相比，显然后者对web站点高并发访问压力下性能的提升更加明显和高效，因此，建议再使用nginx的proxy_cache来缓存web的静态文件以实现web站点性能的提升。